In the summer of 1947, Ansel Adams and his 14-year-old son, Michael, undertook a six-week journey through Alaska that would have notable consequences for the history of conservation. Adams was already close to a household name for his masterful landscape photography, particularly the powerful shots of Yosemite Valley. A 1941 visit to Glacier National Park had sparked his interest in the north country. “Imaginatively inclined,” Adams recalled in his autobiography, “I felt Alaska might be close to the wilderness perfection I continuously sought.” On this relatively short trip, he would take one of his most iconic photographs and do much to encourage Americans of all stripes to visit Alaska and persuade them of the value of the National Park System.

From San Francisco he and Michael drove up U.S. Highway 101 to Seattle, where they boarded the SS Washington for Juneau by way of the Inland Passage, stuffing themselves on buffet food, just as had the pioneer preservationist John Muir decades earlier. A convulsion of thunder and bolt of lightning enthralled them, as if witnessing a divine fireworks display. “I was deeply affected by my first glimpse of the northern coasts and mountains,” recalled Adams. “The rain did not depress me; it was clean and invigorating, and the occasional glimpses of far-off summits gave promise of marvels to come.”

He did not travel light. Wherever he went, he took his large 8-by-10-inch camera, lenses, filter sets, Graflex cameras, and three specially designed pods—in all, a roster of accessories that would fill a page.

Eager for the publicity that Adams could bring, Gov. Ernest Gruening put a two-engine Grumman Goose amphibious plane at his disposal—though the pilot, a wildlife officer, having endured decades of wind, rain, and dizzyingly high altitudes, called it “the Flying Coffin.” After a shaky takeoff, Ansel and his son’s nerves steadied. They were soon enjoying low passage over the coastal waters, coming down in bays where their pilot inspected commercial fishing craft to ensure that the crews hadn’t exceeded catch limits. The gadget-loving Adams was fascinated by the instrument panels; the cockpits of planes flying the coastal areas were quite different from those operating in the interior and the Arctic. From this bird’s-eye view, he took a series of distant color shots of Mount Saint Elias Floating in the Clouds. These “personal” photos remained, as late as 2010, in Michael Adams’s private collection, never shown to the general public. (Some of them are here published for the first time.)

However deep he ventured into the wilderness, Adams often wore a Brooks Brothers sports jacket, white shirt, and plain tie; he didn’t like people turning native. His broad, balding forehead was perhaps his most recognizable feature. The well-trimmed beard suggested a tweedy college professor. Alaskans soon learned that the ever-alert Adams was a master at interpreting the landscape’s endlessly shifting moods; he would break off conversations to point out the droop of a cloud, the sudden fierceness of the sun. The Earth had been created long ago in the flash of a starburst, he thought, and his calling was to turn the Creator’s awesome intensities into framable high art. “The quality of place, the reaction to immediate contact with earth and glowing things that have a frugal relationship with mountains and sky,” he wrote, “is essential to the integrity of our existence on this planet.”

In Juneau and Fairbanks, many stories would be told of Adams’s Goose slipping into remote Alaskan inlets. The six- to eight-passenger plane regularly put down on lakes and bays for Adams to compose brilliant snapshots. He ordered his pilots to swoop toward the ground so he could capture fine angles on sunsets and wildfires. One afternoon the plane nearly crashed when the right landing gear malfunctioned. But as he had predicted, that particular death-defying maneuver helped find the perfect pink and purple rose light, which infused the blue/green/gray/white landscape with unforgettable grace. “We crisscrossed the Coast Range many times, exploring deep valleys, lakes, passes, and peaks,” Adams wrote. “The shadows lengthened and the golden light on the snowy mountains intensified.”

A great photographer will spend weeks, even months, in search of the perfect picture. Shooting Mount McKinley presented a particularly formidable challenge, its immensity stubbornly denying any access to its secrets. The perpetually snowcapped, wind-bitten, 20,000-foot peak simply defied the power of Adams’s 35 mm Contax lens. Even given perfect conditions of light, shadow, and wind, a photographer would find it hard indeed to capture such bulk, however wide the lens. It would demand extreme patience and the ability to shake off the dizziness that thin air often causes. But Adams took joyfully to the rock and ice giant. He did not want so defining a photograph to be taken from the air but rather to capture the spiritual essence of the entire Denali wilderness from the ground. Because McKinley is three times higher than Yosemite’s Half Dome, he figured that it would be thrice as difficult to capture its ultimate image in a photograph.

Everything about the mountain proved difficult. On the train ride to McKinley Station, for example, a steady rain made the rails slippery, and the engineer almost collided with a full-grown moose. “The rain finally stopped,” Adams wrote later, “the rails dried, and the brakes worked. We passed several busy repair crews; the melting permafrost frequently causes the rails to sag, creating a continuous maintenance problem.”

Eventually they crawled into the McKinley Station diner for a meal that tasted of cardboard. At night, mosquitoes filled the air. The Adamses were tired even before their adventure had begun, but after a good night’s sleep, they headed 90 miles into Mount McKinley National Park in a flatbed Ford truck with camera equipment piled in back. They had been given the key to the ranger station at Wonder Lake near the mountain’s base, only to discover that bears had broken into the storage bin and eaten huge boxes of U.S. Army K-ration chocolate. “It was a kick to me as a kid to see the muzzle imprint of a bear on the window glass,” recalled Michael. “They had made quite a mess.”

To get a feel for Wonder Lake, the Adamses hiked a steep switchback trail where the wind bore down with a vengeance. Curiously, the remote landscape reminded them both of the desert conditions of Death Valley. As a connoisseur of light, Adams was keenly aware of changes in the weather, wind velocity in particular. Now, swatting bugs at one in the morning and dealing with the strange reality of the midnight sun, he felt the pressure to accomplish the unprecedented.

They found an ideal panoramic view from just above Wonder Lake. Adams set up the tripod, but it was still difficult to determine the best angle for the shot, while the right light would last only for two or three minutes. For a photographer seeking the perfect frame, sometimes in rain and fog, this was an ordeal. “The scale of this great mountain,” reflected Adams, “is hard to believe.”

He complained in his letters of the insistent rain. Visibility was awful. Vast clouds of mosquitoes descended upon them, even insinuating themselves between film and lens. When Adams developed his photos, many had thus been ruined by the insects, which showed up like cartoon airplanes within the frame. Adams was “disgusted” with himself for not being able to shoot the perfect picture. But the self-flagellation was unwarranted. One of his black and whites—Mount McKinley and Wonder Lake—would be acclaimed as a true modern masterpiece, easily the equal of his Monolith, the Face of Half Dome and Clearing Winter Storm. Taken on an 8-by-10 format camera with a telephoto lens at a 23-inch focal length, Mount McKinley and Wonder Lake shows the mountain and a few swiftly moving clouds to a shifting, otherworldly effect. The overall grayness, the slight blurring, and the vast spread of snow melt all seemed heaven-sent. Adams had hit his mark.

Michael never forgot the moment when his father shot that iconic photograph. With their tripod set and doused in citronella against the bugs, they waited for the right moment, sheltered by a few stunted spruces and embraced by that nearly perfect silence peculiar to Alaska. Quiet and untouched, McKinley asserts a rock-hard permanence. Clouds shift rapidly around its summit; looking up at it for too long can induce motion sickness. Michael remembered the moon glow and the palette of colors that swirled at dawn and dusk. From their ridge, they waited patiently for the flashing moment when, as Jack Kerouac would declare, everything becomes understood. All around them rolled the tundra; and over Wonder Lake the ripples reflected and distorted light. It was hard to tell whether the light was falling or rising. “We both knew the moment,” said Michael. “It was really something special. We had been to a lot of national parks, seen a lot of sights, but this was beyond amazing.”

Of course, the act of judging art contains a high degree of personal taste. Nobody has a monopoly on judgment. But it is safe to say that in Mount McKinley and Wonder Lake Adams produced one of the greatest modern landscape photographs. He managed to make North America’s tallest mountain a fitting sequel to the surrounding wilderness. The contrast between peak and lake is fundamental, its tonal effect seeming naturally to subordinate mountain and sky to the lake.

In the 1930s Adams had perfected his “zone system,” a pragmatic method of achieving high vision by “controlling exposure, development, and printing, incisively translating detail scale, texture, and tone into the final image.” This process became his preoccupation. Briefly put, Adams had professionalized the art of capturing the changing nature of light as it sweeps over a landscape. “The zone system is designed to eliminate guesswork,” explains Robert Hirsch in Seizing the Light: A History of Photography, “and give photographers repeatable control over their materials so that the outcome can be predicted (that is, previsualized).”

Years later, Adams revealed that he had debated whether to use a red 25A filter but ended up going with a deep yellow 15, which served to suppress foreground shadows. In total, Adams shot three fine 8-by-10 images of Denali. Half an hour later, at 2 a.m., clouds had enveloped the peak, and the light no longer radiated so expressively off the lake below. Night at last descended on the summit. Adams would bring off other impressive compositions over the coming years—Rock and Surf (1951) and Moon and Half Dome (1960)—but none ever matched the haunting presence of his 1947 masterpiece.

At his retrospective at San Francisco’s Museum of Modern Art in June 1949, the Alaskan photographs aroused much excitement, especially Mount McKinley and Wonder Lake. Everyone seemed to agree that the McKinley shots displayed a rare originality: minimalism meshing with romanticism among the forlorn Alaska Range. Like Muir before him, Adams employed his photographs to encourage tourists to visit Alaska with their own cameras in hand. He wanted everyone to experience the national parks. As a newly hired consultant for Polaroid, Adams urged amateurs, the core of the conservation movement, to attempt to capture Mount McKinley and Glacier Bay for themselves. The rewards of Alaska, he would tell students at his Yosemite workshops, were life-changing. As the new oracle of the Sierra Club and a true disciple of Muir, he knew that only seeing Alaska could lead to saving the last frontier. Elaborating on Horace Greeley’s “Go West, young man,” he urged the postwar generation to “Go to Alaska, folks, and bring a camera.” Influenced by Adams, American families started spending summer vacations in such national parks as Mount McKinley and Glacier Bay.

Adams had opened up interior Alaska to tourists as never before; the money was in nature photography and recreation, not the extraction industries. A new postwar generation was seeking to get away from the suburban doldrums and to rediscover the American wilderness. “You must be able to touch the living rock, drink the pure water, scan the great vistas, sleep under the stars, and awaken to the cool dawn wind,” wrote this pioneer. “Such experiences are the heritage of all people.”